Why do guys give more attention to a side girl rather than someone who's actually worth it?

I was dating someone for 6 years. And I'm between he had his affairs with a lot of different women. Recently I found out he was seeing someone while he was dating me. We broke up 8 months ago. And he continues to talk to this knowing she was cheating on her baby daddy ass well. Why do men to do this? I'm confused why do men rather be with a hoe than a real women? Someone please answer this!